Concrete floors typically include a series of separate individually poured or cast-in-place adjacent concrete slabs. Concrete floors can also be made up of concrete slabs that are formed from larger concrete slabs that are individually poured or cast-in-place. Such concrete slabs that are formed from such larger concrete slabs are often made by employing or forming one or more contraction joints in the larger concrete slabs. Contraction joints (which are also sometimes called control joints) are used to control naturally or randomly occurring cracking in concrete floors from stresses caused by concrete shrinkage, thermal contraction, moisture or thermal gradients within the concrete, and/or various external forces on the concrete floors. Contraction joints are typically formed by vertically cutting the concrete floors along or at the area of the desired location of the contraction joint. Contraction joints are typically vertically sawed into the concrete and often extend approximately one third of the way through the depth of the concrete. When larger concrete slab cracks along the contraction joint, the smaller adjacent concrete slabs are formed.
It should be appreciated that the term concrete slab as used herein is meant to include a separately individually poured or cast-in-place concrete slab or a concrete slab formed from a larger concrete slab.
U.S. Pat. No. 7,334,963 discloses a joint stabilizing apparatus having an expandable cylindrical housing that can be inserted into a cylindrical hole drilled at a “loose joint” at or between two adjacent concrete slabs. This joint stabilizing apparatus limits relative vertical displacement between the two adjacent concrete slabs. More specifically, the hole is drilled downward into the concrete, centered on the plane of a lateral opening/joint at or between the adjacent concrete slabs. This expandable cylindrical housing includes two rigid semi-circular housing halves. This joint stabilizing apparatus is oriented inside of the circular hole such that the two housing halves are on opposite sides of the centerline of the lateral opening/joint. The housing halves are pushed apart by turning a threaded bolt inside of the housing. Turning the bolt causes two bi-laterally symmetric wedge blocks to draw towards each other, and pressing the bearing surfaces of the wedge blocks against inclined surfaces inside of the respective housing halves. As the housing halves are pushed apart, the outside surfaces of the expandable housing engage the adjacent walls of the adjacent concrete slabs formed by the drilled hole and apply opposing horizontal compressive forces to the adjacent concrete slabs. Friction between the expandable housing and the adjacent concrete slabs limits or prevents the adjacent concrete slabs from vertically moving relative to each other.
The apparatus disclosed in U.S. Pat. No. 7,334,963 has multiple moving parts that typically require the apparatus to have a certain size and outer diameter, which in turn requires a similarly-sized hole to be drilled in the adjacent concrete slabs. There is a need to improve the joint stabilizing apparatus disclosed in U.S. Pat. No. 7,334,963 by making it simpler and by providing an option for an apparatus with a smaller size outer diameter.